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Looks like what you are trying to do is a numerical root-solving operation. D9 is the variable and E11 is the calculated result. You want Excel to automatically find the value of D9 for which E11 equals E10, where E10 is 0.5.
A normal Excel formula cannot do this if E11 already depends on D9. You cannot put a formula in D9 that simply says "change D9 until E11 = E10" because that creates a circular reference. Goal Seek works because it is an iterative calculation engine outside the normal worksheet formula calculation.
However, you can do this with a formula if you express the calculation currently performed in E11 as a function of a candidate value for D9. A formula can then perform its own iteration, for example with LET and a binary-search algorithm:
=LET(target,E10,low,0,high,1000,iterations,50,REDUCE(0,SEQUENCE(iterations),LAMBDA(x,_,LET(mid,(low+high)/2,result,[calculation using mid],IF(result>target,mid,mid)))))
The exact formula depends on how E11 is calculated from D9 and the values in E19:E616.
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hth
Marcin